in the Compounds of Zinc and Antimony. 223 
of definite proportions, and that this change was not accompanied 
by any alteration of crystalline form. A similar variation of com- 
position was afterwards observed in the crystals of Sb Zne, and 
it is the object of the present paper to describe the law of the va- 
riation in both cases and to explain its cause. 
n the course of my investigations on this subject, crystalliza- 
tions were made or attempted of alloys differing in composition 
by one half to five per cent., according to circumstances, from the 
alloy containing 95 per cent. of zine to that containing 95 per 
cent. of antimony ; but only two crystalline forms were observed, 
that of Sb Zns and that of Sb Zn2. Well defined crystals, like 
those described under Sb Zn2 in the former paper,* were ob- 
tained from the alloys between 43 and 60 per cent. of zinc; and 
ing point of antimony is much above that of zinc, the fluid zine 
acted on the solid antimony as a solvent, dissolving the pure 
metal, but not the impurities, which rose to the surface forming 
C This scum seemed to take with it some of the anti- 
mony and thus caused a loss, which, together with the impurity, 
was found by experiment to be about three per cent. of the an- 
timony used. This resulted in raising the per-centage of zine in 
the alloy at most about eight-tenths of one per cent. The alloys 
below 43 per cent. of ziric were made by melting the antimony 
first, and then adding zinc. By this method the loss of antimony 
as very greatly diminished, and, counting the impurity, was 
found to be only about one per cent. and a half of the antimony 
used. In preparing the alloys this loss was always allow ” 
and the crystallizations were all made as nearly as possible under 
the same circumstances, so that any unexpected cause of error 
should affect all equally. The crystals formed in the alloys were 
all analyzed in my laboratory under my direction and immediate 
Supervision, and the greater part of them by myself. The rest 
Were by my assistants, Mr. F. H. Storer, Mr. C. W. Eliot, and 
Mr. C. S. Homer, to whose care and accuracy I take pleasure 
in bearing witness. ‘Their work is in all respects as reliable as 
my own. The results are collected in the following table which 
will explain itself. 
* This Journal, vol. xviii, p. 234. 
